Many mobile devices include global navigation satellite system (GNSS) technology to determine the location of the mobile device. The most commonly used GNSS is the global positioning system (GPS). Present GPS technology works well in relatively unobstructed environments that provide direct line-of-sight to GPS satellites in the sky. However, in urban environments with high-rise buildings, the mobile devices may fail to derive their locations due to partial satellite visibility. Alternatively, even if the mobile devices do determine their location, the location errors tend to be very large. These large accuracy errors tend to diminish the value of the location for various purposes.